Gas sensor having insulator assembly for supporting heater

Abstract

There is provided a gas sensor that includes a sensor element, a heater that comprises an electrode, a housing that holds the sensor element therein, an insulator assembly that surrounds a part of the heater and is constituted of a plurality of insulators, an electric terminal member that is located between the one of the plurality of the insulators and the electrode of the heater, a cover that covers the insulator assembly, a holder for holding the insulator assembly, and an elastic member that is located between the holder and the cover to generate elastic force which is applied at least to the one of the plurality of the insulators to pinch the heater between the one and another one of the plurality of the insulators via the holder so as to bring the electric terminal member into constant electric contact with the electrode of the heater.

1 . A gas sensor having a base end and a distal end opposite to the base end along a center axis of the gas sensor, comprising:
 a sensor element that produces a signal indicating a concentration of a gas;   a heater that heats up the sensor element and has a length having a base end nearer to the base end of the gas sensor than the distal end of the gas sensor along the center axis of the gas sensor, comprising:
 a base end section that is located near the base of the heater; and 
 an electrode that is disposed on an peripheral surface of the base end section; 
   a housing that has a base end nearer to the base end of the gas sensor than the distal end of the gas sensor and a through-hole in which the sensor element is held;   an insulator assembly that surrounds the base section of the heater and is constituted of a plurality of insulators;   an electric terminal member that is located between one of the plurality of the insulators and the electrode of the heater;   a cover that covers the insulator assembly and has an inner wall surface;   a holder for holding the insulator assembly, the holder being arranged between the insulator assembly and the cover; and   an elastic member that is located between the holder and the inner wall surface of the cover to generate elastic force which is applied at least to the one of the plurality of the insulators to pinch the heater between the one of the plurality of the insulators and another one of the plurality of the insulators via the holder so as to bring the electric terminal member into constant electric contact with the electrode of the heater.   
   
   
       2 . The gas sensor according to  claim 1 , wherein the elastic member is joined to the holder. 
   
   
       3 . The gas sensor according to  claim 2 , wherein the elastic member is a spring integrally formed on the holder. 
   
   
       4 . The gas sensor according to  claim 3 , wherein the insulator assembly is composed of two insulators. 
   
   
       5 . The gas sensor according to  claim 3 , further comprising:
 the electric terminal member generates no elasticity.   
   
   
       6 . The gas sensor according to  claim 1 , wherein
 the cover further comprises an interior projection section that is inwardly projected from the inner wall surface of the cover at a position to which spring is touched to apply the elastic force to press the inner wall surface of the cover.   
   
   
       7 . The gas sensor according to  claim 3 , wherein the cover further comprises an interior projection section that is inwardly projected from the inner wall surface of the cover at a position to which spring is touched to apply the elastic force to press the inner wall surface of the cover, 
   
   
       8 . The gas sensor according to  claim 1 , wherein
 the insulator assembly has a length, and   the heater is in contact with the insulator assembly at a plurality of points positioned on a plurality of peripheries having different length from the base end of the heater each others.   
   
   
       9 . The gas sensor according to  claim 3 , wherein
 the insulator assembly has a length, and   the heater is in contact with the insulator assembly at a plurality of points positioned on a plurality of peripheries having different length from the base end of the heater each others.   
   
   
       10 . The gas sensor according to  claim 1 , wherein
 the insulator assembly is composed of two insulators,   one of the plurality of the insulators has a stopper wall and a projecting section to which the electric terminal member is locked so as to bring one of surfaces of the electric terminal to be in contact into with the heater, so that the one of the surfaces of the electric terminal and the stopper wall being in contact with the heater, and   another of the plurality of the insulators has a pinching surface and a stopper wall, the pinching surface and the stopper wall being in contact with the heater, and   the elastic force has a component thereof which is applied in a direction parallel to both the stopper surfaces of the one of the plurality of the insulators and the another one of the plurality of the insulators to form the insulator assembly from the one of the plurality of the insulators and the another one of the plurality of the insulators and to pinch the heater, so that the heater is pinched between the one of the surface of the electric terminal locked to the one of the plurality of the insulators and the pinching surface of the another one of the plurality of the insulators.   
   
   
       11 . The gas sensor according to  claim 3 , wherein
 one of the plurality of the insulators has a stopper wall and a projecting section to which the electric terminal member is locked so as to bring one of surfaces of the electric terminal to be in contact into with the heater, so that the one of the surfaces of the electric terminal and the stopper wall being in contact with the heater, and   another of the plurality of the insulators has a pinching surface and a stopper wall, the pinching surface and the stopper wall being in contact with the heater, and   the elastic force has a component thereof which is applied in a direction parallel to both the stopper surfaces of the one of the plurality of the insulators and the another one of the plurality of the insulators to form the insulator assembly from the one of the plurality of the insulators and the another one of the plurality of the insulators and to pinch the heater, so that the heater is pinched between the one of the surface of the electric terminal locked to the one of the plurality of the insulators and the pinching surface of the another one of the plurality of the insulators.   
   
   
       12 . A gas sensor having a base end and a distal end opposite to the base end along a center axis of the gas sensor, comprising:
 a sensor element that produces a signal indicating a concentration of a gas;   a heater that heats up the sensor element and has a length having a base end nearer to the base end of the gas sensor than the distal end of the gas sensor along the center axis of the gas sensor, comprising:
 a base end section that is located near the base of the heater; and 
 an electrode that is disposed on an peripheral surface of the base end section; 
   a housing that has a base end nearer to the base end of the gas sensor than the distal end of the gas sensor and a through-hole in which the sensor element is held;   an insulator assembly that surrounds the base section of the heater and is constituted of a plurality of insulators;   an electric terminal member that is located between the one of the plurality of the insulators and the electrode of the heater;   a cover that covers the insulator assembly and has an inner wall surface;   a holder arranged between the insulator assembly and the inner wall surface of the cover, further comprising:
 means for holding the insulator assembly; 
 means for generating elastic force which is applied at least to the one of the plurality of the insulators to pinch the heater between the one of the one of the plurality of the insulators and another one of the plurality of the insulators via the holder so as to bring the electric terminal member into constant electric contact with the electrode of the heater. 
   
   
   
       13 . The gas sensor according to  claim 12 , wherein
 the insulator assembly is composed of two insulators,   one of the plurality of the insulators has a stopper wall and a projecting section to which the electric terminal member is locked so as to bring one of surfaces of the electric terminal to be in contact into with the heater, so that the one of the surfaces of the electric terminal and the stopper wall being in contact with the heater, and   another of the plurality of the insulators has a pinching surface and a stopper wall, the pinching surface and the stopper wall being in contact with the heater, and   the elastic force has a component thereof which is applied in a direction parallel to both the stopper surfaces of the one of the plurality of the insulators and the another one of the plurality of the insulators to form the insulator assembly from the one of the plurality of the insulators and the another one of the plurality of the insulators and to pinch the heater, so that the heater is pinched between the one of the surface of the electric terminal locked to the one of the plurality of the insulators and the pinching surface of the another one of the plurality of the insulators.   
   
   
       14 . The gas sensor according to  claim 12 , wherein
 the holder has an insulator holding portion having a substantially cylindrical shape having a slit along the center axis of the gas sensor, and a spring which is formed on a outer surface of the insulator holding portion serving as the means for generating elastic force.